1. Field of the Invention
The present invention relates to a measurement probe to be connected to an optical measurement apparatus that applies measurement light to a living tissue, and estimates the properties of the living tissue based on a measurement value of the measurement light reflected and/or scattered back from the living tissue.
2. Description of the Related Art
Backscattered light in the backward direction from a relatively weak scattering medium such as a living tissue is conventionally known to be observed as enhanced backscattering light according to the degree of spatial coherence (spatial coherence) of the illumination light (see Young L. Kim, et. al, “Low-coherence enhanced backscattering; review of principles and applications for colon cancer screening” Journal of Biomedical Optics, 11(4), 041125 Year 2006). A spectral information measurement technique using this phenomenon is called LEBS (Low-coherence Enhanced Backscattering Spectroscopy), and the relationship between angular pattern of enhanced backscattering and the optical properties of the scattering medium are studied well (see V, Turzhitsky, et. al, “Characterization of Light transport in Scattering Media at Subdiffusion Length Scales with Low-Coherence Enhanced Backscattering” IEEE journal of selected topics in quantum electronics, Vol. 16, No. 3, 619 (2010)). The scattering mean free path (the inverse of the scattering coefficient) is correlated with a change in the internal structure of the scattering medium and is used to detect minute changes in the tissue structure such as those observed in cancer in the early stage. For example, it is known that the use of the profile of enhanced backscattering light enables the identification of colorectal cancer (see Hemant K. Roy, et. al, “Association between Rectal Optical Signatures and Colonic Neoplasia: Potential Applications for Screening” Cancer Research, 69(10), 4476 (2009)).
In the above-mentioned LEBS, a technique is known which applies LEBS to non-invasive measurement in the body through a measurement probe inserted in an endoscope (See U.S. Patent Publication No. 2009/0009759). In this technique, in order to acquire an enhanced backscattering light, illumination light is applied to a living tissue from a distal end of an illuminating fiber of the measurement probe. A plurality of light receiving fibers is used to measure the intensity distribution of scattered light at a plurality of scattering angles. Accordingly, the properties of the living tissue are detected.